Quit it. It was 32 Gb used (i.e. all of it, maybe 1-2 G left for cache) plus 5-6 G of swap.

I don't know how your OS X works, but mine tends to not go into swap before running out of ram. It does not come out of swap when ram is freed indeed, but when you freshly boot it it will stay at swap used: 0 bytes until someone posts too many cat pictures in Slack or Discord.

Or until i forget how many VMs I opened, but that's work and actually useful.

Edit: I can't reply to your reply because HN doesn't like so many indents. I also don't want to continue a flame war about observed behaviour vs the theory of shared libraries and memory mapped files etc so I'll stop here.